Abstract Detail

Wood water storage creates a potentially important buffer plants can tap into during the periods of water stress. Yet, trees vary significantly in the quantity of stored water and the degree to which they make use of it. Stored water can contribute from 6 to as much as 50% of the daily transpiration requirements of a tree. We currently do not have a clear understanding of structural drivers of water storage. Two candidate wood tissues can potentially store water: parenchyma and fibers. They are the two most abundant tissues, together making up a majority of the wood volume. The primary functions of parenchyma is thought to be carbohydrate and water storage, whereas the primary function of fiber is thought to be mechanical support. However, recent, indirect evidence suggests that fibers may play a pivotal role in water storage, potentially compromising mechanical strength. We examined hydraulic, anatomical and mechanical traits in twigs of 30 temperate, deciduous tree species grown in the Arnold Arboretum of Harvard University. The species represented a broad phylogenetic range (30 genera from 23 families) and diverse wood anatomies. Their wood density ranged from 0.34 to 0.71 g cm-3 and was correlated with midday leaf water potential (two-fold variation from -1.1 to -2.5 MPa). As expected, species with higher density wood tended to tolerate more negative midday water potentials. However, these species also had higher midday relative water contents (ranging from 39% to 81%). This suggests that high density species maintain water contents closer to their maximum capacity to store water, whereas the midday water contents of low density species rarely approach their maximum storage capacity. Given that wood density is an outcome of anatomical structure, water storage strategies among species are likely underpinned by differences in their wood anatomy. In this talk, I will explore how these strategies might be driven by parenchyma and fiber properties, and how they relate to mechanical strength.